To adhere a plurality of materials, a method of applying an adhesive to the surfaces (joining surfaces) of the materials, and then drying and curing the adhesive has been known. The adhesion principle of this method is mainly mechanical adhesion, physical adhesion, or chemical adhesion.
Mechanical adhesion is an adhesion using anchoring effects. An adhesive applied to a material surface enters into the irregularities of the surfaces and serves as an anchor, thereby adhering the materials.
In physical adhesion, a material surface is wet with an adhesive, thereby adhering the materials by the intermolecular force between the adhesive molecules and the molecules of the material surfaces.
Chemical adhesion is made by a chemical reaction between components in an adhesive and components in the material surfaces.
However, since these adhesion methods use adhesives, they have a drawback of easy detachment of the adhered materials from the joining surfaces. Further, once the materials are adhered, the materials cannot be returned to the state before adhesion; that is, it is impossible to control the adhesion. Additionally, since these adhesion methods require an adhesive, components other than the materials are present between the joining surfaces; thus, the methods have a drawback of possible adverse effects from these components.